cafeamericainmag.com
There has been a lot of CW discussion on climate change. This is an article written by someone that used to strongly believe in anthropogenic global warming and then looked at all the evidence before arriving at a different conclusion. The articles goes through what they did.
I thought a top-level submission would be more interesting as climate change is such a hot button topic and it would be good to have a top-level spot to discuss it for now. I have informed the author of this submission; they said they will drop by and engage with the comments here!
Jump in the discussion.
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Notes -
Reading through the article I quickly found a couple errors in reasoning. Also overall the writing style doesn't give the impression that the author is deeply knowledgeable in the subject (or in heat transfer generally). Mostly this is unconvincing to me.
The author gives insinuates that this somehow violates the laws of thermodynamics, but it doesn't. I can't tell if he doesn't understand this or is being intentional misleading.
Take two black body radiatiors at different temperatures and places them near each other. Would you say that the lower temperature body radiates in every direction /except/ the side facing the hotter? Of course not. While the net heat flow will be from hotter to colder, it is totally reasonable to talk about energy transfer from colder to hotter as a matter of accounting.
For 2263 w/m2 solar irradiance, 0.7 albedo, 0.85 emissivity, Venus "Should" only have a surface temperature of less than 200c, instead of the 400+c we observe. Internal heating of Venus appears to be negligible (10s of mW/m2 at the surface).
Venus can be explained by a thicker atmosphere and thus a larger adiabatic lapse rate effect. Also see: https://www.themotte.org/post/960/the-vacuity-of-climate-science/203479?context=8#context . It's just not a good demonstration of GHE.
As to the thermodynamics, the arguments are plentiful. I'll just point out two physicists believed that it does violate the 2nd Law and published a peer-reviewed paper to that effect (Gerlich & Tscheuschner). Most others, of course, disagree. The point in the article is that rather than debate it, let's demonstrate it experimentally, in the real world - and this has not been done for the GHE.
Your linked post mentions nothing about adiabatic lapse rate nor how it can explain Venus' temperature being much higher than would be predicted from blackbody equilibrium. Care to explain in detail what you mean?
The linked post is meant to show that using Venus to corroborate a model is foolish, as that same reasoning was used to predict it had the same temperature as Earth. It provides just as much support to any more modern theory, namely, none at all.
For an adiabatic lapse rate on Venus description see: https://youtube.com/watch?v=_4KG0-2ckac ,
After admonishing me for comparing model predicted temperatures of Venus to observation, you link me to a video where the adiabatic lapse model is compared to observations, asserts without independent evidence that this fully explains venus' surface temperatures, and what's more tries to generalize this to earth. This is unsound logic by your own argument.
In any case, I would appreciate it if you would explain your position to me in text, here, rather than sending me links. Or at least provide additional commentary along with the link. After watching that video I am no closer to understanding how adiabadic lapse rate results in surface temperatures in excess of blackbody nor why I should favor this over the greenhouse effect.
Sure. The grand canyon is a good starting point. The temperature at the bottom of the canyon is hotter than at the top. Why is that? It's not due to the greenhouse effect. It's due to earth's adiabatic lapse rate.
Essentially, gravity pulls air in the atmosphere downwards, doing work to compress it, which increases its pressure and temperature. The hotter air then starts expanding and rising (being displaced by the cooler air being brought down), which causes it to cool and decrease in pressure. This is an ongoing process. Notably, it has nothing to do with any radiative properties of the atmosphere (i.e. the greenhouse effect). It can be calculated from basic values of the mass of air and gravity: https://phys.libretexts.org/Bookshelves/Thermodynamics_and_Statistical_Mechanics/Heat_and_Thermodynamics_(Tatum)/08%3A_Heat_Capacity_and_the_Expansion_of_Gases/8.08%3A_Adiabatic_Lapse_Rate .
The lapse rate is essentially the same on Venus as on Earth, and as Venus's atmosphere is thicker than Earth, the lapse rate has a longer way to go, resulting in a higher temperature increase. It must be noted the pressure on Venus's surface is 90x that of Earth's.
The blackbody calculation presumes no atmosphere and thus no adiabatic lapse rate. The presence of an atmosphere and gravity introduces this mechanism by which work is done, heating the air as it compresses and gets close to the surface. It explains the tropospheric temperature gradient and, it must be re-iterated, has nothing to do with any radiative properties of the air. Any atmosphere, even one without any greenhouse gases whatsoever, would have this feature.
The question then is: as the adiabatic lapse rate explains the grand canyon temperature difference, why would it not also explain the temperature difference between the surface and the effective blackbody temperature? It must be noted the effective temperature of Earth (255K, -18C) is indicative of the average amount radiated by an entire column of surface plus atmosphere above. As we've established there must be a gradient due to the lapse rate, the average of this column must necessarily be somewhere in the middle. Below is hotter, above is cooler.
This doesn't make any sense to me. The adiabatic lapse rate describes how the temperature would change if you took a parcel of air, did not allow it to exchange heat (that's the adiabatic part, right?) and moved it up or down so it expands or contracts. As pressure increases or decreases, so does temperature.
But in the Grand Canyon, if gravity is pulling cooler, denser air down, and letting warmer, less dense air rise (as must happen), that's going to result in a cooling effect, not a warming effect. Yes, the cooler air may get a bit more compressed as it falls, and thus rise a little in temperature, but you're also losing warm air that was even warmer when it was at the same altitude, so air circulation would result in a net loss of heat. If you have two regions of air at the same altitude and one is warmer, it will have a rising force compared to the other. Gravity can't make it fall relative to the other one. (To be precise, they could both be rising or falling, just that the cooler one will always fall relative to the warmer one, unless there's momentum of air coming in from outside the system and interacting with the geometry of the landscape, like winds blowing across the canyon).
Gravity is not pulling air downward in a thermodynamics-violating way. If we started out with an atmosphere that was not in steady state, where it was a lot more diffuse and bigger than it should be, then yes, as gravity pulled it down and compressed it, it would get warmer. But that would only happen once (or rather it would oscillate like a spring for a while but eventually settle down).
So yeah, I don't get this at all. I don't know if the temperature gradient at the Grand Canyon is completely due to the greenhouse effect, but I'm pretty sure it's not anything to do with what you're saying, unless I'm misunderstanding you.
Consider the air at the elevation level at the top of the grand canyon. The air that is at ground level at this elevation (eg past the top rim of the canyon) will have a certain temperature. If the grand canyon didn't exist but were equally flat with this ground level, the air there would be the same temperature, right? This is the equilibrium at that height.
Now bring the grand canyon back into existence and allow that air to fall. What happens? As it falls, gravity compresses it, and thus heats it up. By the time it reaches the ground it will be hotter. On its way down, this falling air will displace the air further below it, causing that air below to rise and, due to the lower pressure, expand and cool on its way back up. Thus you have a circulating effect, with the equilibrium temperature increasing with depth.
It doesn't violate thermodynamics as gravity is doing work on the gas, converting potential energy to kinetic energy and increasing its temperature on the way down, while via buoyancy pushing the lower, warmer air up. With no further energy inputs the whole column of air would gradually cool (and eventually freeze and fall out of the sky), but the sun provides the "seed" energy by warming the surface which then warms the air via conduction & convection.
Without the lapse rate basically all ground-level air at any elevation would be the same temperature, the temperature achieved by the sun's warming -- with perhaps mountains slightly warmer as they are closer to the Sun. But the lapse rate additionally causes this effect of warmer air below and cooler air above.
You don't have to take my word for it! Some links:
"You can thank a weather phenomenon called adiabatic heating. As air sinks down into a lower elevation, it gets compressed, compressed air releases heat as energy. This caused the air mass to become even warmer.".
https://edition.cnn.com/2020/06/24/weather/arizona-california-heat-forecast-grand-canyon-shoes-trnd/index.html
"In adiabatic cooling, when a mass of air rises—as it does when it moves upslope against a mountain range—it encounters decreasing atmospheric pressure with increasing elevation. The air mass expands until it reaches pressure equilibrium with the external environment. The expansion results in a cooling of the air mass.
With adiabatic heating, as a mass of air descends in the atmosphere—as it does when it moves downslope from a mountain range—the air encounters increasing atmospheric pressure. Compression of the air mass is accompanied by an increase in temperature."
https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/adiabatic-heating
"Air molecules play a pivotal role in temperature variation with elevation. When at a low elevation, there are more air molecules compressed together due to the weight of the atmosphere pressing down. As these air molecules are compressed, they generate heat, leading to a temperature increase. Conversely, as elevation rises, air molecules spread apart due to decreased atmospheric pressure, leading to a temperature decrease."
https://science.howstuffworks.com/nature/climate-weather/atmospheric/question186.htm
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